This non-provisional application claims priority under 35 U.S.C. § 119(a) from Korean Patent Application No. 2002-84268 filed on Dec. 26, 2002, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a novel organic semiconductor polymer and an organic transistor using the same, and more particularly to a composite-structured polythienylthiazole derivative in which thiazole rings having a high electron affinity, i.e. n-type semiconductor properties, are incorporated with thiophene units having p-type semiconductor properties, thereby exhibiting both p-type and n-type semiconductor properties.
2. Description of the Related Art
Recently, the use of low molecules, e.g., pentacene, as organic semiconductor materials has been actively researched. On the other hand, special attention has been paid to high molecules focusing on polythiophenes. The high molecules are attractive due to their low charge mobility and processability, compared to the low molecules. In addition, since the high molecule organic semiconductor materials can be applied in the form of solutions, unlike the low molecules, they can be formed into thin films by screen-printing, ink-jet and roll-printing techniques. Such high molecule organic semiconductor materials are useful in fabricating large area transistors on plastic films at low cost.
Cambridge Univ., Seiko Epson Corp., Philips Corp., etc. have already fabricated test products of high molecule organic thin film transistors employing a polythiophene-based material, e.g., P3HT (Poly(3-hexylthiophene) or F8T2 (a copolymer consisting of dioctylfluorene and bithiophene (ratio of 8:2)). These organic thin film transistors (hereinafter, referred to as “OTFT”) have a low charge mobility of around 0.02 cm2/Vs, which does not come up with pentacene as noted above, but do not require a high working frequency and can be fabricated into thin film transistors at low cost. For commercialization of OTFTs, important parameters, such as an acceptable on/off current ratio, as well as high charge mobility, must be satisfied. Specially, to improve the on/off current ratio, the off-state leakage current must be reduced to the lowest possible extent. Many attempts have been made to improve these properties in various ways. Research teams from Lucent Technologies Inc. reported improved results in parameters of OTFT devices by using a combination of an n-type inorganic semiconductor material and a p-type organic semiconductor material as an active layer (U.S. Pat. No. 5,625,199). However, there is no merit in fabrication process when compared to the conventional silicon-based TFT processes and this is not suitable for mass-production of OTFT devices. As such, high molecular weight OTFTs that satisfy the requirements of high charge mobility and low current loss at off-state, have not hitherto been reported.